Hydraulic circuits for machine tools



Feb' 14, 1950 R. E. HERRSTRUM ETAL, 2,497,608

HYDRAULIC CIRCUITS FOR MACHINE TOOLS Filed May l5, 1947 6 Sheets-Sheet 1 Feb. 14, 1950 R. E. HERRSTRUM ETAL 2,497,608

HYDRAULIC CIRCUITS FCR MACHINE TooLs Filed May 15, 1947 6 Sheets-Sheet 2 Feb. 14, 1950 R. E. HERRSTRUM ETAL 2,497,608

HYDRAULIC CIRCUITS FCR MACHINE 'rooLs Filed May 15, 1947 6 sheets-sheet 5 Feb. 14, 1950 R. E. HERRSTRUM ETAL. 2,497,608

HYDRAULIC CIRCUITS FCR MACHINE TooLs Filed May 15, 194? 6 Sheets-Sheet 4 Feb. 14, 1950 R. E. HERRSTRUM -:TAL u 2,497,608

HYDRAULIC CIRCUITS FOR MACHINE TOOLS Filed May l5, 194'?l 6 She'ets-Sheet 5 Feb. 14, 1950 I R. E. HERRsTRuM ETAL 2,497,608

HYDRAULIC CIRCUITS FOR MACHINE TOOLS Filed May 15, 1947 l 6 Sheets-Sheet 6 Patented Feb. 14, 195o HYDRAULIC CIRCUITS FOR MACHINE TOOLS Rudolph E. Herrstruin and Stanley A. vBjorklund, Rockford, Ill., assignors to Rockford Machine Tool Company, Rockford, Ill., a corporation of Illinois Application May 15, 1947, Serial No. 148,254

11 Claims.

This invention relates to hydraulic circuits, and more particularly to a hydraulic circuit for a, hydraulic machine tool.

It is a general object of this invention to provide a hydraulic circuit for machine tools of the shaper or planer class of improved construction and arrangement.

It is a further object of the invention to provide in a machine tool of the class described, a hydraulic circuit including two pistons for the re-y ciprocation of the table or platen.

Another object of the invention is to provide a hydraulic circuit embodying a-single acting and a double acting piston to reciprocate the table or. platen.

Yet another object of the invention is to providea two cylinder hydraulic motor adapted to be used in conjunction with a positive displacennt variable volume pump for reciprocating the a le.

n Another object of the invention is to provide in a hydraulic machine tool of the class described, a two piston motor arrangement for reciprocating the table having `at least three forward cutting speeds. l

A further object of the invention is to provide for a rapid return stroke of the reciprocating table regardless of the speed of the cutting stroke.

Another object of the invention is to provide for. three cutting speeds and three return stroke speeds in a hydraulic circuit of the class described.

Other and further objects of the invention will become apparent of the following description and drawings in which y Fig. l'is a view partly broken away for clarity of illustration, of a planer table; and, I

Figs. 2 to 11,' inclusive, are diagrammatic views of the hydraulic motor and hydraulic circuit for reciprocating the table.

While our invention is susceptible of embodiment in many different forms, we have shown in the drawings and will herein describe in detail one such embodiment, with the understanding that the present disclosure is to be considered as an exemplication of the principles of the invention and is not intended to limit the invention to the embodiment illustrated. The scope of the invention will be pointed out in the appended claims. f

Hydraulic machine tools of the shaper or planer class commonly employ a hydraulic circuit` to direct operating hydraulic iluid to `one orm more piston and cylinder devices toreciprocate the table or cutting member. The inven tion hereinafter described is adapted forv use with the type of machine tool mentioned and embodies a novel hydraulic circuit for` supplying operating hydraulic fluid to two piston and cylinder devices. The first such device comprises a cylinder having a double acting piston reciprocable therein, the second cylinder having a single acting piston reciprocable therein. In the preferred embodiment, the single acting piston has a diameter equal to the diameter of the piston rod of the double acting piston so `that the volume of hydraulic fluid displaced by the single acting piston and the rod end of the double actingv piston is precisely equal to the vol. ume displaced by. the other end of the double acting piston. Valve means are provided to direct operating fluid to vboth or either of the cylinders to present three different areas to operating hydraulic fluid circulated by a variable volume reversible pump, and thereby giving three cutting speeds as Well as three cutting force areas for each setting of the pump volume. If the volume of the pump is varied, an innite number of speeds can be had within each cuttingforce range. Valve means are also provided so that a high return speed can `be vhad at all times.y This feature is particularly desirable in a planer because, the return of the table being a noncutting stroke, the non-productive time is reduced to a minimum. Other advantages over conventional double acting pistons are that the device is less costly and a much better pip-ing arrangement can be made from both the appearance and cost viewpoint, and inasmuch as hy-` draulic fluid is directed to the rodend of the double acting piston on the cutting stroke, the heavy load places the piston rod in tension and thereby eliminates rod deflection such as would be received when a long rod is in compression.

`While the invention is susceptible of many embodiments, it will be described herein as embodied in a planer which comprises a base 20 upon which is mounted a reciprocating platen or table 2| adapted to be reciprocated upon ways 22 by means of a two cylinder hydraulic motor 23.

Referring now to Fig. 2, 25 indicates a cylinder having a piston 26 reciprocable therein. Attached to the piston is a connecting rod 2,1 extending through the left hand end of the cylinder 25, as viewed in Fig. 2. A second cylinder 28 is provided with a single acting piston 29 to which the connectingrod 30 is connected. Both connecting rods 21 and 30 are attached to the reciprocating table 2| of the planer. Hydraulic iiuid under pressure is supplied to the cylinders and 28 through a hydraulic circuit, which will be hereinafter more fully explained from a reversible pump 3|.

The hydraulic circuit can best be described by referring vto the figures which show the circuit and the various methods of operating the circuit. In the drawings, long arrows are used to designate fluid under pressure, short arrows to denote return uid and dotted arrows to indicate static pressure. On the low speed cutting stroke, illustrated in Fig. 2, hydraulic fluid under pressure is delivered by the pump 3|v .to a conduit 32, which connects to a stop and start valve 33.

The valve 33 is provided with a bore 34 having a valve slidable therein. The valve has an extension 35 extending from the bore to provide.

a manually adjustable lever for shifting the valve to its various positions. The valve has two end portions 36 and 31 and a single intermediate land 38 providing two reduced portions 39 and 4|] between the land '38 and the end portions. The valve body is further provided with annular grooves 4|, 42, 43, 44 and 45.

As can be seen, hydraulic fluid under pressure is delivered from the conduit 32 to the annular groove 42, reduced portion 39 to the annular groove 43 and thence into a conduit 46 to a high return valve 41.

The high return valve 41 comprises a bore 48 having a valve slidable therein, the valve being provided with two end portions 49 and 50 and an intermediate land 5|. Two reduced portions 52 and 53 are provided Ybetween the central land and the end portions. The valve body is further provided with annular grooves 55, 55, 51, 58 and 59 and 59a.

Fluid under pressure from the conduit 45 is delivered to the annular groove 5! and thence to a passage Bil connecting with the speed selector valve 5|. The selector valve comprises a bore 62 having a valve slidable therein, the valve being provided with a portion |53 extending beyond the valve body to provide means for mov* ing the valve to various speed positions which will be hereinafter described. The speed selector valve 5| has two end portions 65 and 66 and a `single land 51. Two reduced portions 58 and 69 are dei-ined between the land and the end portions. The speed selector valve is also provided with the annular grooves 163, 1l, 12, 13 and B3, the annular groove 1| being connected with the annular groove 55 of the high return valve bymeans of a passage 14, the annular groove 12 connecting with the yannular groove 51 by passage 50, as previously described, and the annular groove 13 connects with the annular groove 58 by'passage 15. The annular groove 59a connects with annular groove 83 by means of passage 16.

The fluid under pressure delivered to the passage Gi! is conducted into reduced portion. |59 of the speed selector valve 6| by the annular groove 12 and thence passes via passage 14, annular groove 55 to a conduit 11 connecting kwith the cylinder 28 which contains the single actingpiston 29. Hydraulic fluid under pressure isk also conducted from the reduced portion 59 via passage 15, annular groove 58, reduced portion. 53, and annular groove 59 to a conduit 18 which conducts the hydraulic fluid to the left hand or rod end of the cylinder 25 containing the double acting piston 26.

The hydraulic circuit, just described with the provide for a cutting stroke with the connect- I ing rod under compression. The areas presented the intake side ci the pump 3i.

by the ,pistons yto the uid pressure are preferably so arranged that two thirds of the force delivered, toy the table is derived from the double acting piston and one third from the single acting piston. Fluid from the right hand end of the double acting cylinder 25 passes by means of a conduit 83 to conduit 8| and annular groove .44 offthe's'top-and go valve, reduced portion 4D, annulargroove 45 and a conduit 82 and back to The diameter of the -piston 28 is exactly equal to the diameter of the connecting r'od21 so that the difference between the areas ofthe two sides of the piston 2'5 in the double acting cylinder is exactly equal to the area of the piston 29. Therefore, the right hand or piston end of l the cylinder 25 delivers precisely the same volume of oil to the intake side of the pump., as is delivered by the discharge side of thepump to the left hand or rod end of that cyiinder and to the single actingcylinder 28.

Shifting the speed selector valve 5| to the position shown -in Fig.`3, provides for a medium out. With the valve in theposition shownin that figure, fluid under pressure is directed from the conduit 45 vtothe annular groove 51, passage Sil. annular groove 12 to the -reduced portion 59. Fluid under pressure Vfrom the reduced portion 55 is thence directed via `passage 15, annular groove V53, reduced portion 53, annular groove 59 to conduit 18 and thence to the left hand or rod end of the cylinder 25. Fluid from the right handlend of the cylinder 25 is returned via conduits B'D'and 8| .to the pump. As iiuid pressure from the discharge side of the pump is being delivered only tothe rod end of the cylinder 2c. more uid is being returnedv from the piston end of that cylinder than is .being discharged by the pump. yThe excess uid is delivered to the single acting piston. 28 by means of annular groove 59a, passage 16, annular groove 83, conduit 84 to annular groove 1|! and thence via reduced portion 68, annular` groove 1|, passage 14, annular groove 55, reduced portion 52, annular groove 55 to the conduit 11 and thence to the cylinder 28. It is apparent, therefore, that precisely the same volume of oil is being returned to the intake side of the pump, as is discharged 'from the discharge side.

By .shifting the speedselector valve 6| further tothe right to the position shown in `Fig. 4.-, a high cutting .stroke is achieved in which .fluid is delivered to the single acting piston only. From an inspection of that figure, ,it can be seen that iiuid under pressure in the conduit 45 passes via annular groove .51, passage 50, .annular groove 1| to the reduced portion 6d. and thence through annulargroove 1B, passage 14 to annular groove 55. The fluid then travels via the reduced portion 5 2, annular groove .55, conduit 11 and into the cylinder 23. Fluid from the right hand end of the cylinder25is in .part returned to the pump and in part conducted tothe left hand end of that cylinder. This latter circuit can be traced through conduit all, passage 16, annular groove 83, reduced portion |59, annular groove12, passage 15, annular groove 58, reduced'portion 53, an-

nular groove 59 and conduit 18 to the rod end of thecylinder 25. Again it is clear that the pump is discharging and receiving identical volumes of oil. ',*With the particular hydraulic circuit which we are disclosing herein, it is possible to achieve a high speed return of the cutting member regardless of the speed of the cutting stroke. It is further possible to achieve return strokes or" varying speeds, if desired.

`If a high speed return stroke is desired, regardless of the speed of the cutting stroke, the high return valve 41 is permitted to remain in the circuit. Referring now to Fig. 5, thespeed selector valve is in the position for a loW speed cutting stroke. Upon reversal of the direction of the pump 3| (which reversal of direction will be hereinafter more fully described), fluid under pressure in the conduit 8| is directed to a conduit 86, through a pilot valve 81 and by means of a conduit 88 to the left hand end of the bore 48 thereby shifting the high return valve to the position shown. At the same time hydraulic fluid under pressure is directed into the conduit 82 through the stop and go valve 33 and into the conduit 8|. The iiuid under pressure is thence delivered to the right hand end of the cylinder 25 by means of the conduit 80. Fluid under pressure is also directed into the left hand or rod end of the cylinder 25 by means of the annular groove 59a, reduced portion 53, annular groove 59 to the conduit 18. Inasmuch as duid pressure is applied to both ends of the cylinder 25, the table moves at a high return speed. As the head end'of the piston presents a greater area to the fluid pressure than does the rod end, the piston will move to the left. Fluid discharged from the rod end ofy cylinder 25 thereby is added tothe uid discharged by the pump to eiect a rapid stroke. Likewise the amount of oil discharged by the pump to effect a return stroke is equal to the volume displaced by the connecting rod 21. As previously explained, the rod 21 has the same area as the piston 29 in the single acting cylinder, and the uid contained in that cylinder is returned to the pump to equalize the volume pumped with the volume received by the pump. As is clearly seen in Fig. 5, this return of oil from the cylinder 28 is effected through' conduit 11, annular groove 55, reduced portion 52, annular groove 56 and conduit 4B.

A high return speed isalso achievable with the speed selector valve set for either the medium or high cut. This feature is illustrated in Figs. 6 and '7. It will be noted v*that with the speed selector valve in either of the positions mentioned',l the high speed return is achieved in a' manner similar to the one previously described With the speed selector valve in low cut position.

If it is desired that the return stroke be at the same speed as 'the cutting stroke, the high return valve may be cut out of the hydraulic system by the pilot valve 81. `Moving the pilot valve 81` to the position shown in Fig. 8 will maintain the high return valve in a position at the left hand end of its bore 48. With the speed selector valve in the low cut position shown in that figure, upon reversal of the pump, iiuid under pressure lis directed to the right hand end of the double act ing cylinder. Fluid from the left hand of that cylinder and from the single acting cylinder isv returned to the pump. With the speed selector valve in the position shown in Fig. 9, a medium return speed is achieved by directing fluid under pressure to the single acting cylinder and to the right hand or piston end of the double acting cylinder. The fluid pumped will have a volume equal to the difference in volume ofthe cylinder andthe piston 29, which volume, of course, equals the volume discharged from the left hand endv ofA the double acting cylinder and a medium return is thereby obtained. i

Upon shifting the speed selector valve to the position for high cut, a high speed return is obtained, as is shown in Fig. 10, wherein fluid prese sure on return is directed to both ends of the double acting cylinder, While the fluid in the single acting cylinder is returned to the pump.`

The reciprocation of the cutting member may be'halted by the stop and go valve 33. Moving that valve to the position shown in Fig. 11, directs hydraulic fluid under pressure from the discharge conduit 32to the annular groove 42 and thence into the return conduit 82 to the intake side oi the pump.

As previously started, the pump 3| is a revers-v` ing pump. A pilot pump 90 directs pilot iluid intov4 a conduit 9| through pilot valve 92 into the auxiliary circuit, generally designated 93. With the pilot valve in the position shown in Fig. 2, uid passes through the valve into a conduit 94 and thence by means of a conduit 95 into a feed piston and cylinder device 96. This device is to impart an intermittent feed motion to the table or Work piece in timed relationship to the reciprocation of the cutting member. Hydraulic fluid is also directed to the right hand end of the reversing cylinder 91 which in normal installation would be positioned on the pump 3| as indicated.. This cylinder has a bore 98 and a piston 99 reciprocable therein. The piston is provided with reversing means |00 to reverse the direction of flow of the main pump 3|.

The reciprocating member of themachine is, provided with dogs ||5 to trip the pilot valve 92 at the end of the stroke of the reciprocating member. Tripping the pilot valve to the position shown in Fig. 5, directs hydraulic uid from the pilot pump 90 into a conduit ||l| to the left hand end of the feed cylinder 96. Fluid is also directed' into the conduit |82 and into the left hand end ofA the reversing cylinder 91 to shift the piston andhence the reversing device |80 to a position re-'Vy versing the direction of operation of the main pump. Pilot pressure in the auxiliary circuit 93 is also directed into a piston and cylinder device,- generally designated |03 for actuating a tool lift-Ql ing device, if desired. This device comprises ya bore |04 having a piston l 85 reciprocable therein; the piston being reciprocated to the right upon pilot fluid pressure being admitted to the conduit |02 and returned to the position shown in Fig. 2 bya spring |06 upon reversal of thedirection of' the flow of the pilot iiuid. 1 l

vDuring the cutting operations, it sometimes becomes necessary when extremely high pressures are used, that the return line be charged'to'" compensate lrior the compressibility or elasticity of' thehydraulic fluid. In other Words, when highpump pressure is directed to the cutting 'force' side of the cylinders, and resistanceis put to`- the reciprocating members, the hydraulic viiuid will compress slightly with the result that vvhenv the tool leaves the Work, the table 'Will have'a I Ltendency to jumlp. We have eliminated this' tendency by adding a resistance pressure lin the return oilline. This is accomplishedr by providing a small supercharge pump Hi! which vde?,` rives oil from the tank and directsituto a" conrhiit` ,toeither the return or discharge sidev oihthe-jv A pump; This delivery to either side of the pump agences;

iswthrough the spring check valves H2 and H3, and is permitted by those valves only upon .cavitation of the oil on .either the cutting or return stroke, Whether such cavitation is due to .cornpression or possible leakage.

We claim:

l. .In a hydraulic machine tool having a reciprocating table, means for reciprocating the table including a closed hydraulic circuit, a pump for circulating hydraulic fluid under pressure in said circuit, a .nrst cylinder in said circuit having a double acting piston reciprocable therein, a single piston rod in said .cylinder and connected tothe piston, a second cylinder in said circuit h aving a single acting piston reciprocable therein, said last mentioned piston having the same diameter as the piston rod and reciprocation of the pistons being adapted to cause reciprocation of the table, a valve in said circuit for selectively directing hydraulic fluid under pressure .to either or both of said cylinders to cause the lsaid pistons to reciprocate therein and means for directing return fluid `from said cylinders to the pump intakeand to the cylinder not receiving uid under pressure.

2f. In a hydraulic machine tool having a reciprocating table, means for reciprocating the table including a closed -hydraulic circuit, a first cylinder having a double acting .piston reciprocable therein, a single piston rod in vsaid cylinder and connected vto the piston, a second cylinder having a single acting piston reciprocable therein, the diametery of the last mentioned piston being equal to the diameter of the piston rod, and reciprocation of the pistons being adapted to cause reciprocation of the table, a pump for supplying fluid under prsure to the cylinders to cause the said pistons to reciprocate therein, valve means in said circuit movable to a first position directing iluid under pressure to the rod `end of the double actingpiston and to the single acting piston to cause a relatively .slow movement of the table in a cutting direction, said valve means being movable to a second position directing fluid under pressure only to the rod end of the double acting piston to cause said table to move at a medium speed in a cutting direction, and `said valve means being movable to a third position directing fluid under pressure only to the lsingle acting piston to cause a relatively fast movement of the table in a cutting direction said valve means directing returniiuid from said cylinders to the pump intake and to the cylinder not receiving fluid under pressure.

3. In a hydraulic machine tool having a reciprocating member, means for reciprocating the member including a hydraulic circuit, a first cylinder having a double acting piston reciprocable therein, and a second cylinder having a single acting piston reciprocable therein, rec-iprocation o-f the pistons being adapted to cause reciprocation of the member, a pumpv for supplying fluid under pressure to the cylinders to cause the said pistons to reciprocate therein, the said fluid .under pressure being supplied to the rod end of the double acting piston on movement of the member ina cutting direction, a vfirst valve means in said circuit movable to a first position .directing fluid under pressure to the rod end of the double acty ing piston and to the single acting piston to cause tbn to cause said table to move at a medium speed.

in a cutting direction, and said valve means being movable to a third :position directing uid under pressure only to the single acting piston to cause a relatively fast movement of the table in a cutting direction, and a Second valve means in said circuit adapted to apply fluid pressure to both ends of :said rst cylinder to cause a rapid movement of the member in a return direction in all positions of said first valve.

4. In a hydraulic machine tool having a reciprocating table, means for reciprocating the table including a hydraulic circuit, a first cylinder having a double acting piston reciprocable therein, `and a second cylinder having va single acting piston reciprocable therein, reciprocation of the pistons being adapted to cause reciprocation of the table, a reversible pump for supplying fluid under pressure to the cylinders to cause the said pistons to reciprocate therein, the said fluid under pressure being supplied to the `rod end of the double acting piston on movement of the table in a cutting direction, a `iirst valve means in said circuit movable to a first position directing fluid under pressure to the rod end of the double acting piston and to the single ,acting piston to cause a `relatively slow movement of the table in a cutting direction, said valve means being movable to a second position directing fluid under pressure only to the rod end of thev double acting piston to cause said table to move at a medium speed in a cutting direction, and said valve means being movable to a third position directing fluid under pressure only to the single acting piston to cause a relatively fast movement of the table in a cutting direction, and a second valve means in said circuit being selectively operable upon reversal of direction of flow of said fluid by reversal of the pump, to direct said fluid to both ends of said rst cylinder to cause a rapid movement of the table in the return direction in all positions of said first valve. and said second valve means being selectively inoperable whereby said reversal of direction of now of said uid is adapted to cause movement of said table in a return direction at the same speed as in the cutting direction as determined by the position of said first valve.

5, In a hydraulic machine tool having a reciprocating member, means for reciprocating the member including a pump, a closed hydraulic circuit, means operating to reverse the direction of flowr of said fluid in said circuit, a rst cylinder having a double acting piston reciprocable' therein and a second cylinder having a single acting piston reciprocable therein, said cylinders being interposed in said circuit and reciprccation of said pistons being adapted to cause reciprocation of the member, a piston rod connected to said double acting piston, said piston rod having the same diameter as the single acting piston, a first valve means in said circuit to direct fluid under pressure from the pump to the rod end of the first cylinder and to the second cylinder to cause movement of the member in a cutting direction, the fluid discharged from the other end of the irst cylinder being returned to the pump intake, and a second valve means in the said circuit adapted upon reversal of the direcv tion of now of said fluid to apply fluid pressure to both ends of said first cylinder to cause a" rapid movement of the member in a return direction, said second valve directing returnA fluid from said second cylinder to the pump intake. 4

6. In a hydraulic machine tool having a reciprocating member, means for reciprocating the member including a pump,-a closed hydraulic circuit, ymeans operating topreverse thev direction of flow of said fluid in said circuit,l a first cylinder having a double 4acting piston., Areciprocable therein, and a second cylinderv having a single acting piston reciprocable thereirrsaid cylinders being interposed in said ,circuit and reciprocation of said pistons being adapted to causereciproca-y tion of the member, a pistonrod connectedto said double acting piston, said piston rod having the same diameter as ,the` ysingle acting piston, a valve means in said circuit rmovableto aflrst position directing fluid under pressure from the pump to the rod end of therstcylinder yand -to the second cylinder. `to ycause relatively, slow movement of the membery in a cutting direction, the fluid discharged from the other end ofgrthe rst cylinder being returned to the pump. intake, said valve means being movable to a secondposition directing fluid under pressure. .only .to the rodend vof the doubleacting: piston .to cause said 4member to 'move at a mediumispeed ,in va cutting direction, the fluid discharged-,from the, other end of the rst cylinder being `'directed toA the second cylinderand to the pump intakeuand said valve means being movable to aiithird posi, tion directing fluid underupressure only to the second cylinder to cause `Jai-relatively fast movement of the table in a cutting direction, fluid from the head end ofy the rst cylinder being directed to the rod end o f the first cylinder and to the pump intake. y v j '7. In a hydraulic machine tool having a reciprocating member, means for reciprocating the member including a pump, a closed hydraulic circuit, means operatingvto reverse the direction of flow, of said lfluid in said circuit, a firstcylinderrv having a double acting: piston reciprccable therein, and a second cylinder having-fasingle acting piston reciprocable thereinfsaid cylinders being interposed in said circuit and reciprocation of said pistonsbeing adapted-,to cause reciprocaf tion of the member, a piston rodconnected to said double acting piston, said piston rod having the same diameter as the single acting piston, a rst valve means in said circuit movable to a first position directing uid under pressure from the pump to the rod end of the first cylinder and to the second cylinder to cause relative slow movement of the member in a cutting direction, the fluid discharged from the other end of the rst cylinder being returned to the pump intake, said rst valve means being movable to a second position directing uid under pressure only to the rod end of the double acting piston to cause said member to move at a medium speed in a cutting direction, the fluid discharged from .the other end of the iirst cylinder being directed to the second cylinder and to the pump intake, and said rst valve means being movable to a third position directing fluid under pressure only to the second cylinder to cause a relatively fast movement of the table in a cutting direction, fluid from the head end of the ilrst cylinder being directed to the rod end of the first cylinder and to the pump intake, and a second valve means in said circuit adapted upon reversal of the direction of flow of said fluid to apply fluid pressure to both ends of said rst cylinder to cause a rapid movement of the member in a return direction, said second valve directing return fluid from the second cylinder to the pump intake.

8. In a hydraulic machine tool having a reciprocating member, means for reciprocating the member including a pump, a closed hydraulic l0 circuit, means operating to reverse the direction offlow of said fluid in said circuit, a first cylinder having a double acting; piston reciprocable there,- in, and a `second,cylinder having a single acting piston reciprocable therein, said cylinders being interposed yin ,said y.circuit and reciprocation of said pistons being adapted to cause reciprocation of the member, a piston rodv connected to said double acting piston, s aid piston rod having the same diameter as the single acting` piston, a rst valve means in said circuit movable to a flrst position directing fluid under pressure from the pump to the rod end of the iirst cylinder andto the second cylinder tn cause relatively slow move-y mentcil the member in a cutting direction, the nuid discharged from the other end of the rst cylinder being returned to the pump intake, said iirstvalve means being movable to a second position directing iluid under vpressure konly to the rod end ofthe double acting piston to causersaid member to move at a medium speed in a cutting direction, the fluid discharged from the other,v end of the rst cylinder being directed to the second; cylinder and to thepump intake, and said rst valve means being movable toa third positionl directing fluid under pressure only to the second cylinder.. to cause a relatively fast movementl of the table in` a cutting direction, fluid from the` head end oi the firstcylinder being-directed' to,v thefrodgend of the iirst'cylinder and to thefpump, intake, and a second valve means vin said circuity beingselectiyely operable upon reversal .'of direction `of flowofv said iluid to applyfluid pressurer to-,botlh :endsof saidv rst cylinder to cause a` rapid movement of the member in a return direczA tion in all positions oirsaid rstvalve, and .said second valve means being selectively inoperable` whereby -saidreversal direction of said flowz-of'v said iluid is adapted to cause movement of the member in a return direction at the same speed: as` inthe cutting direction as v determined by the.. position of said first valve. 1w z ;9Ilnar hydraulic machine tool havingialre-c ciprocating table, means for reciprocating the table including a reversible pump, a closed hydraulic circuit, a flrst cylinder having a double acting piston reciprocable therein, and a second cylinder having a single acting piston reciprocable therein, said cylinders being interposed in said circuit and reciprocation of said pistons being adapted to cause reciprocation of the member, a piston rod connected to said double acting piston, said piston rod having the same diameter as the single acting piston, a rst valve means in said circuit to direct fluid under pressure from the pump to the rod end of the first cylinder and to the second cylinder to cause movement of the member in a cutting direction, the iluid discharged from the other end of the rst cylinder being returned to the pump intake, and a second valve means in the said circuit adapted upon reversal of the direction oi flow of said fluid to direct uid under pressure to both ends of said iirst cylinder to cause a rapid movement of the member in a return direction, said second valve directing return fluid from said second cylinder to the pump intake, an auxiliary hydraulic circuit, means for circulating hydraulic fluid under pressure in said auxiliary circuit, a pilot valve adapted to be actuated by means on the table to reverse the direction of ow of fluid in said auxiliary circuit, and means in said auxiliary circuit to re verse the said pump on reversal of direction of flow of fluid in the auxiliary circuit.

10. In a vhydraulic machine tool having a re-,

cilib'c'ting table;l meansy for reciprc'catin'g` the table; including a reversible pump, a'.I closed hydraulic circuit, a rst cylinder having a double acting piston re'c'iprocabler therein; and aI second cylinder having a single'-actingpistonreciprocable therein, saidl cylindersV being interposed in said circuit'l and reciprocation of saidv pistonsI bei-ng adapted to cause reciprocaton of the mem-ber, a piston rod connected' to said double acting pistn, said piston rod having the same diameter as the' single acting piston, a first valve means in said circuiti to direct fluid under pressureV from the pump to the rod end f thel rst cylinder and te the second cylinder to cause movement off the me'lmlaer` in a cutting direction,` the uid disd charged? from the other end of the' r'stcylirid'er Being returned to the` pump' intake, and a second valve means in the'- saidcircuit adapted upon ree versalof the direction of new: of said fit1-id to direct fluid-'under pressure td beth ends of said r'st cylinder to cause a rapid movement of the meniina return direction, said second valve di-4 recting return fluid from saidsecond cylinder to: the pump intake',- an` auxiliary' hydraulic circuit, means for circulatingl hydraulic? lid under pressure in said auxiliary circuit, a r'st piston and cylinder device interposed in said auxiliarycircuit adapted to` be reciprocated upon. reversalof di rectionof ow in said circuit',- the reciprccation or said piston being adapted to reverse' the said pump' anda second pistonv and cylinder device in said auxiliary' circuit adapted4 to be reciprccated upon reversal of direction' ci flow' of said iiuid tol eiect intermittent feed motio'ii of a Workv carry-f ing member.

11. In a hydraulic machine teol having' a reciprocating member, means for reciprocating the member including a pump',- a closed mainhy: draulic circuit, means; operating to reverse the direction of now of said fluid in said circuit, a first cylinder having a double acting pistenl `re`v ciprocable therein and a se'cnd cylinder having a single acting pistn reciprocable' therein, said cylinders' being interposed in said circuit and reciprocation offsaid pistons being' adapted tocause reciprocation oi the member, a piston rod connected t'oi said double acting piston, said piston rod having the same diameter as the single acting piston, a= first valve means'in said circuit to direct uid under' pressure" from the pump to the rod e'nd ofthe iii-St cylinder and to the second cylinder tol causel movementof the member ina cutting direction, the iluid discharged from the other' en'd oi the first'y cylinder being returned to' the pump intake, and a second valve means in the said circuitlr afda'lzt'edr upon reversal of the direction of flow ofsaid fluid toA apply uid pressure' to both ends of saidv firstl cylinder to cause a rapid movement of the member in a return direction, said second valve directing return fluid from'l said second cylinder" to the pump intake, a make-up iiuid4 circuit, a supercharge pump in said circuit coinnectable with said main circuit to supply make-up fluid thereto upon cavitation of hydraulic fluidin the main circuit, and valve means responsive' to an excess of fluid pressure in said make-up circuit over the fluid pressure in the main circuit to admit make-up nuid to said main circuit.v

RUDOLPH E. HERRSTRUM. STANLEY A. B'JORKLUND.

REFERENCES CITED The' following references are of record in the file of this patent:

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